GB958287A - A method of obtaining complete combustion of fluent fuel and an apparatus for carrying out such method - Google Patents

Abstract

958,287. Returning combustion products to furnaces; burners. COMBUSTION ENGINEERING Inc. Sept. 29, 1961 [Dec. 2, 1960], No. 35338/61. Headings F4B and F4T. Steam generating apparatus includes a furnace for burning a mixture of fluid or pulverulent fuel and air and means for recirculating a mixture of air and exhaust gases to the furnace, the amount of exhaust gases in the mixture being variable. In the embodiment of Fig. 1, exhaust gases from tangentially fired furnaces 2 and 4 pass over steam tubes lining the furnace, a superheater 6, a reheater 8 and an economizer 10 and thence pass through air preheaters 22 to a stack 23. A portion of the gases is withdrawn through ducts 14 containing dampers 21 and blowers 16 and passed through connections 18 into ducts 28. Combustion air is blown by fans 20 through air preheaters 22 into ducts 24 and thence through ducts 26 inside and concentric with ducts 28 to the furnace burners 40. Air from ducts 24 also passes into ducts 28 and mixes with the exhaust gases therein, this mixture also being passed to the burners 40. Fig. 2 illustrates the layout of a burner unit as seen from inside the furnace. Fuel issues through openings 42 or 44 which are surrounded by openings 46 through which primary combustion air from ducts 26 issues. The mixture of exhaust gases and air from ducts 28 pass through openings 48 above and below the openings 46. The proportion of exhaust gases recirculated is controlled either manually or automatically by the dampers 21. Fig. 4 shows a modified burner comprising ducts 104 for the injection of liquid fuel and 108 for the alternative injection of gaseous or pulverulent fuel surrounded by a primary air duct 110 provided with helical ribs 116. A mixture of recirculated furnace exhaust gases and air is admitted to a duct 130 surrounding duct 110 through passages 112 which contain dampers 122 to impart a swirling motion to the mixture and to control the amount of the mixture admitted. The dampers are pivoted on shafts 123 and are adjusted through arms 124 connected to an operating ring 125.